diff --git a/app/helpers/participants_helper.rb b/app/helpers/participants_helper.rb
index 7059f83..e4afa3a 100644
--- a/app/helpers/participants_helper.rb
+++ b/app/helpers/participants_helper.rb
@@ -1,2 +1,7 @@
 module ParticipantsHelper
-end
+    def mask_ssn(ssn)
+        return '' if ssn.blank?
+    
+        "*****#{ssn[-4..-1]}"
+      end
+    end
\ No newline at end of file
diff --git a/app/views/participants/show.html.erb b/app/views/participants/show.html.erb
index ad2cbee..b1471eb 100644
--- a/app/views/participants/show.html.erb
+++ b/app/views/participants/show.html.erb
@@ -39,7 +39,7 @@
 
           <p class="card-text">
             <strong>SSN:</strong>
-            <%= @participant.ssn %>
+            <%= mask_ssn(@participant.ssn) %>
           </p>
 
           <p class="card-text">